1. Field of the Invention
The present invention relates to a numerical controller, and in particular, relates to a numerical controller that can eliminate the need for a skip signal and a key operation when coordinates of an object to be measured are acquired.
2. Description of the Related Art
When workpiece is machined by controlling a machine tool, it is necessary to measure the position of the workpiece placed in a machining area of the machine tool to set a workpiece coordinate system of the workpiece to be machined. In addition, it is necessary to measure dimensions of tools mounted on the spindle to set a tool offset amount.
As a conventional technology to measure a coordinate value of an object to be measured, for example, as disclosed in Japanese Patent Application Laid-Open No. 05-066820 A, there is a known method of bringing a touch sensor (probe) into contact with a workpiece by mounting the touch sensor on an axis moving portion of a feed axis of a machine tool and controlling the feed axis to drive, and acquiring a coordinate value by stopping (skipping) the drive of the feed axis by a skip signal input at this point to measure a coordinate value of the object to be measured based on the acquired coordinate value.
When the measuring method of a coordinate value using a skip signal as described above is adopted, however, a probe to detect contact needs to be prepared and also a mechanism to input a skip signal when the probe detects contact needs to be prepared, leading to a high price and posing a problem in terms of cost.
As another conventional technology, as shown in FIGS. 9A to 9C, a method of using a centering bar 3 is disclosed in Japanese Patent Application Laid-Open No. 2002-116016. The centering bar 3 includes, as shown in FIG. 9A, a fixed sleeve 4 and an eccentric sleeve 5 and is used by mounting the portion of the fixed sleeve 4 on the spindle of a machine tool. When the position of a workpiece is measured, as shown in FIG. 9B, the spindle is rotated while a central axis of the eccentric sleeve 5 is decentered from a rotary axis of the spindle (central axis of the fixed sleeve 4) and, as shown in FIG. 9C, the centering bar 3 is brought closer to a workpiece 6 by a key operation of a control panel. Then, a coordinate value of the spindle is acquired while visually checking that the deviation between the central axis of the fixed sleeve 4 and the central axis of the eccentric sleeve 5 has been eliminated by contact of the eccentric sleeve 5 of the centering bar 3 with the workpiece 6 being brought into contact and a coordinate value of an object to be measured is measured based on the acquired coordinate value.
When the measuring method of a coordinate value using a centering bar as described above is adopted, however, the operator needs to visually check the centering bar while operating a control panel and to perform key input work to set the coordinate value while viewing a screen after decentering is eliminated, which requires movement of line of sight and hands among the centering bar, screen, control panel, and keyboard, thereby posing a problem of increased burdens of the operator with increased trouble.